Solving for x with A, b, and c Given

  • Thread starter Thread starter Toby_Obie
  • Start date Start date
Click For Summary
SUMMARY

The discussion centers on the difficulty of isolating the variable x in the equation A = bx / (1 - (1 + x)^-c). Users express that there is no simple solution for this equation, particularly for values of c greater than or equal to 4, where it becomes increasingly complex. A participant mentions using Excel's Goal Seek function to approximate x for known values of A, b, and c, achieving results accurate to four decimal places. The consensus is that while a general solution may not exist, numerical methods can provide practical approximations.

PREREQUISITES
  • Understanding of algebraic manipulation and rearranging equations
  • Familiarity with exponential functions and their properties
  • Basic knowledge of numerical methods for solving equations
  • Experience using Excel, specifically the Goal Seek function
NEXT STEPS
  • Research advanced algebraic techniques for solving non-linear equations
  • Learn about numerical approximation methods, including Newton's method
  • Explore Excel's Goal Seek and Solver functions for optimization problems
  • Study polynomial equations and their solvability, particularly for degrees higher than four
USEFUL FOR

Mathematicians, students studying algebra, data analysts using Excel for problem-solving, and anyone interested in numerical methods for approximating solutions to complex equations.

Toby_Obie
Messages
18
Reaction score
0
Hello,

Im trying to rearrange to find x from the below (all other values, A, b and c known)

A = bx / 1-(1+x)^-c

Below denominator ending reads (1+x)^(-c)

I've rearranged but to no avail, I'm unsure how to isolate x

Any input much appreciated

Thanks
 
Physics news on Phys.org
Hello Toby! :smile:

(you needed to put the index in curly brackets, {-c}, since it had more than one character … alternatively, try using the X2 tag just above the Reply box :wink:)

This is the same as (1 + x)-c = 1 - (b/A)x …

I don't think there is a "simple" solution.

But why are you looking for one?
 
Noted

I've never come up against an equation like this before, just curious whether it can be solved for x ? (new skills)

Is there a general solution to this type of equation ?

Can you point me in the right direction ?

Thanks very much
 
Toby_Obie said:
Is there a general solution to this type of equation ?

I don't think so.

Real life just isn't that convenient! :redface:
 
Thanks anyway

Anybody else think they know the answer ?
 
Really, the problem is very complicated to solve, and for most c\geq 4 it's likely impossible to solve!

There is a proof that says for polynomials of degree 5 or higher, there is no way to solve the equation in its general case like quartics and below have been.
 
Okay

I'm using Excel to approximate x for known values of A, b, c

Thanks anyways
 
Just a note

Excel Goal Seek function solved my function to 4 decimal places, good tool
 

Similar threads

  • · Replies 19 ·
Replies
19
Views
3K
Replies
11
Views
2K
Replies
16
Views
2K
  • · Replies 21 ·
Replies
21
Views
3K
Replies
18
Views
3K
Replies
3
Views
2K
Replies
19
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 22 ·
Replies
22
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K